Posted by: Rob Viens | June 23, 2012

The Stupendous Pleasures of the Atlantic Coastal Rainforest

On June 23rd, Darwin once more, “went to the forest, which so often has been proved so fruitful in all kinds of animals.” At the time he thought it was his last visit to the Brazilian rainforest, though it turned out not to be the case.  Nonetheless it evoked some pretty powerful feelings for him:

“It is in all probability the last time I shall ever wander in a Brazilian forest.— I find the pleasure derived from such scenes increases, instead of as might have been expected, diminishing. To day instead of the rude tracks, I followed a brook, which in a narrow ravine flowed amongst the huge granitic blocks.— No art could depict so stupendous a scene.— the decaying trunks of enormous trees scattered about, formed in many places natural bridges; beneath & around them the damp shade favoured the growth of the Fern & Palm trees.—& looking upwards the trees in themselves lofty, thus seen, appeared of an almost incredible height.— I soon found even by creeping, I could not penetrate the entangled mass of the living & dead vegetation.— On coming out of the forest, the effect without any exaggeration is that of the full light of the sun breaking on a person who has just left a darkened room.” (June 23)

As always, I am particularly fond of the colorful way in which he describes the forest – “so stupendous a scene” that it rivals an artists attempt to capture it; his ever-increasing “pleasure” each time he comes back; the image of the “darkened” forest floor, full of  “natural bridges” and an “entangled mass of living and dead vegetation”; and the “enormous trees” of “incredible height”.  Art may be able to do it justice, but Darwin’s words are enough to make one feel like they are almost there.

Atlantic Rainforest (from the World Land Trust)

Atlantic Rainforest

The forest that Darwin has been visiting (for his entire time in Brazil) is part of the bioregion known as the Atlantic Coastal Rainforest. In Darwin’s time this forest was already being cut down for agriculture and pastureland, though when the Portuguese first set foot in Brazil it is estimated to have covered between 1.0 and 1.5 million square kilometers. Sadly today it only covers 4,000 square kilometers, and only a fraction of that is primary forest (never been cut or burned by humans).  The loss of over 93% of this forest ecosystem makes this one of the most endangered biomes in the world. (Only Madagascar has a higher loss rate.)

Location of the Atlantic Coastal Rainforest today (red) and 500 years ago (green) – less than 7% of the forest remains intact (from the Atlantic Rainforest Institution)

Region of the Atlantic Rainforest

This loss comes at a great cost, because the Atlantic Rainforest also contains a tremendous amount of biodiversity.  One study suggests there are over 20,000 plants alone (40% of which are endemic to only this region).  Another states that 60% of the vertebrates in the region are endemic. In a study by the Atlantic Rainforest Institution (ARFI) they found:

“In Southern Bahia (where the ARFI base camp is located) there were following counts recorded in only one hectare (size of a football field): 270 species of mammals (90 endemic), 372 amphibious (260 endemic), 197 reptiles (60 endemic), 849 birds (188 endemic), 2120 butterflies (948 endemic) and a world record of 456 trees.” (Atlantic Rainforest Institution website)

And new species – from invertebrates to plants to monkey’s and sloths – are being discovered every year. We really have no idea what we are losing.

Golden Lion Tamarin – one of the highly endangered primate species of the Atlantic Rainforest (from the World Association of Zoos and Aquariums)

Golden Lion Tamarin

One of the reasons the Atlantic Rainforest is so biologically diverse is that it covers an area with a lot of geographic diversity. The bioregion runs from sea level to the crest of the coastal mountains (about 3000 m / 10,000 ft) and spans about 25° of latitude.  It starts in the mangrove and dense forests along the shoreline, passes through regions of intense rainfall (over 2 m a year), and extends into the westernmost seasonal forests that have a distinct dry season. It might seem that it should be connected to the Amazon Rainforest; however, there is a large dry region that separates the two forests, making it difficult for species to move between the two regions.  Hence, each tends to be rather unique.

Natural vegetation zones of Brazil – note the tan region that separates the Atlantic Coastal Forest from the Amazon (from NASA):

Brazil vegetation zones

Darwin primarily experienced invertebrates in the forest, even lamenting to John Henslow in a letter regarding the specimens he was sending back to England from Brazil:

“I am afraid when I do send it, you will be disappointed, not having skins of birds & but very few plants, & geological specimens small: the rest of the things in bulk make very little show.” (Correspondence to John Henslow, June 1932)

However, the forest is also full of amazing mammals, birds and amphibians – they were probably not as prominent in the circumference of day trips Darwin took around Rio.  These include some rare mammals, such as the:

Maned Sloth – Bradypus torquatus (from Focus on Nature Tours):

Maned sloth

Thin-spined porcupine – Chaetomys subspinosus (from Lonely Planet Images):

Thin-spined porcupine

Considering his awe and excitement about being in the forest, I can only imagine what Darwin would have to say about the loss of such a diverse and beautiful forest.  I think it would break his heart. (RJV)

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Responses

  1. […] meters (6,600 feet).  Their elevation helps lend biodiversity to the Atlantic Coastal Forest (see The Stupendous Pleasures of the Atlantic Coastal Rainforest), and partially in recognition of this the region around the mountains was protected as a National […]


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